To solve this problem, we use the **skid mark formula** which relates the speed of a vehicle to the length of its skid marks: **Speed (mph) = √(30 × d × f)** where: - **d** = length of skid marks (in feet) - **f** = coefficient of friction (usually ranges from 0.7 to 0.8 for dry asphalt; let's use 0.75 as a typical value) Given: - **d = 84 feet** - **f = 0.75** (typical for dry asphalt) Now, plug in the values: Speed = √(30 × 84 × 0.75) Speed = √(30 × 63) Speed = √(1890) Speed ≈ **43.5 mph** **So, the speed of the vehicle before the brakes were applied was approximately 43.5 mph** (assuming a coefficient of friction of 0.75). If you have a different road condition, the coefficient may change. Let me know if you need the calculation for wet roads or other surfaces!